The invention is based on a fuel injection pump for internal combustion engines as generally described hereinafter. In known injection pumps equipped with a constant pressure relief valve (Swiss Pat. No. 394,710 corresponding to U.S. Pat. No. 3,195,465), the spring of the relief valve is supported via a threaded element which is secured in the sheath-like section of the valve closing body. The disadvantage of this screw connection is that because it may loosen, reliable functioning of the injection pump is not always assured, because parts of the valve may fall into the pump work chamber and cause grave damage to the injection pump as well as attendant damage to the engine itself.